Realistic Aluminum Material In Cycles?
Here's my latest render.  I'm not fully satisfied with it yet, but it's close.



Here is the node setup:


Click to enlarge.

It's basically an Anisotropic shader with a little bit of straight gloss, then a very light Fresnel component.  I then used a stretched noise texture to mix in a very small amount of diffuse (to make some cracks more pronounced) and apply a bump.  I've also created the below node group for a very fine grain, which is also used for bump mapping.



Note: the Translate and Scale group nodes are homemade equivalents of the corresponding parts of the mapping node.  They are explained here.

Like I said, I'm not quite happy with it yet.  In particular the flat end needs better texture coordinates for a circular bump (I'm having trouble creating a procedural radial blur) and the inside needs less anisotropy.